The present invention relates to a magnetoresistance effect element, a manufacturing method of a magnetoresistance effect element, a magnetic head and a magnetic reproduction apparatus, and more particularly, it relates to a magnetoresistance effect element where a sense current flows perpendicularly to the film plane, a manufacturing method of the magnetoresistance effect element, and a magnetic head and a magnetic reproduction apparatus including the magnetoresistance effect element.
Although a magnetic storage density of HDD (hard disk drive) is improved dramatically in recent years, it has been desired to raise the magnetic storage density further. Since a record bit size becomes small as the magnetic storage density is raised, a reproducing sensitivity is lowered in the conventional thin film head. Therefore, now, the magnetoresistance effect type head (MR head) including a magnetoresistance effect (MagnetoResistive effect) has been used mainly. A spin valve (spin-valve) type giant magnetoresistance type head (SVGMR head) which shows a big magnetoresistance effect has attracted attention.
FIG. 29 is a schematic diagram which illustrates the outline section structure of the spin valve film. That is, the spin valve film 100 has the structure in which a ferromagnetic layer F, a non-magnetic layer S, a ferromagnetic layer P, and an antiferromagnetic layer A are laminated in this order.
The non-magnetic layer S is interposed between the two ferromagnetic layers F and P which are in a magnetically uncoupled state. Magnetization of one ferromagnetic layer P is fixed with an exchange bias using the antiferromagnetic material A, and whereas the magnetization of other ferromagnetic layer F is able to rotate easily by an external magnetic fields (signal magnetic field etc.). And a giant magnetoresistance effect can be obtained by rotating only magnetization of the ferromagnetic layer F by an external magnetic field and changing its magnetic orientation relative to that of the other magnetic layer (Phys. Rev. B, Vol.45, 806 (1992), J. Appl. Phys. Vol.69, 4774 (1991)).
Here, the ferromagnetic layer F is called a “free layer”, a “magnetic field reception layer”, or a “magnetically free layer”, the ferromagnetic layer P is called a “pinned layer”, a “magnetically pinned layer” or a “magnetically fixed layer”, and the non-magnetic layer S is called a “spacer layer”, “a magnetic coupling interception layer”, etc. in many cases.
In the case of the spin valve film, since magnetization of the free layer F, i.e., a ferromagnetic layer, can be rotated also in the lower field, it is possible to raise reproduction sensitivity and it is suitable for MR element for MR heads.
In the case of such a spin valve element, it is necessary to pass the “sense current” in order to detect a change of the resistance caused by a magnetic field.
For this reason, the method of passing the sense current in parallel to a film plane and measuring resistance of a parallel direction to a film plane is generally used. Generally this method is called the “CIP (current-in-plane)” system.
In the case of the CIP system, the value of about 10% through 20% can be obtained as a change rate of MR. Moreover, in the MR head of the shield type used currently, the spin valve element is used in the plane shape almost near a square. Therefore, it is considered that the resistance of MR element is equal to the resistance of MR film plane. For this reason, in the spin valve film of a CIP system, a good S/N characteristic can be obtained by making the resistance of the film plane into 5 ohms through 30 ohms. Resistance of this level can be easily made by making the thickness of the whole spin valve film thin. Therefore, generally the spin valve film of the CIP system is used as the MR element for MR heads currently.
On the other hand, the magnetoresistance effect element (hereafter called a “CPP type artificial lattice”) where the sense current is passed perpendicularly (current perpendicular to plane: CPP) to the film plane in the artificial lattice in which a magnetic material and a non-magnetic material are laminated is proposed as a method of obtaining big MR which exceeds 30%.
In a CPP type artificial lattice type magnetoresistance effect element, the electrode is provided in the upper and lower sides of the artificial lattice in which the ferromagnetic layers and the non-magnetic layers are laminated by turns, and the sense current flows perpendicularly to the film plane. With this structure, since the probability that the sense current crosses a magnetic layer/non-magnetic layer interface becomes high, an interface effect can be obtained and big change rate of MR can be obtained.
However, in using MR element for an MR head, it is necessary not only to control the magnetization of a magnetic layer and to enable it to measure an external magnetic field efficiently by it, but also to form each magnetic layer into a single magnetic domain so that a Barkhausen noise etc. may not occur simultaneously. However, as mentioned above, it is necessary to laminate magnetic layers and non-magnetic layers repeatedly by turns in order to earn resistance in the case of the CPP type MR element, therefore, it is technically very difficult to individually control the magnetization of each of such many the magnetic layers.
On the other hand, the CPP system can be adopted also in the spin valve structure using FeMn/NiFe/Cu/NiFe, FeMn/CoFe/Cu/CoFe, etc.
That is, the sense current is passed perpendicularly to the film plane of the laminated films which have a spin valve structure. However, since the number of pinned layers and free layers becomes much smaller than that of the artificial lattice type, the resistance falls further and a resistance rate of change also falls.
As for this point, the magnetoresistance effect element in which the non-magnetic film which consists of the mixture of an insulator and an electric conductor is inserted is proposed in Japanese Patent No.3293437.
The CPP type magnetoresistance effect element in which the non-magnetic film which has the structure where an insulator I surrounds the electric conductors C is inserted is disclosed in FIG. 1 of Japanese Patent No.3293437. However, as the example of the structure of the non-magnetic film disclosed in Japanese Patent No.3293437, there is only an explanation that non-magnetic films having thickness of 2 nm or 5 nm was deposited by using the multi-component target including Al2O3 and Cu, and it is unknown what kind of structure was made concretely as the non-magnetic film.
As explained above, various structures, such as a spin valve film of a CIP type, an artificial lattice of a CPP type, and spin valve film of a CPP type have been proposed. However, the present magnetic storage density is continuing the rise of an annual rate of 60% or more, and the further output increase has been desired. However, the spin valve film which can be used with high storage density which exceeds 100 Gbits/inch2 at present and which has suitable resistance and the big amount of MR change, and serves as high sensitivity magnetically is difficult to realize.